// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef UI_GFX_WIN_SINGLETON_HWND_H_
#define UI_GFX_WIN_SINGLETON_HWND_H_

#include <vector>
#include <windows.h>

#include "base/macros.h"
#include "base/observer_list.h"
#include "ui/gfx/gfx_export.h"
#include "ui/gfx/win/window_impl.h"

namespace base {
template <typename T>
struct DefaultSingletonTraits;
}

namespace gfx {

class SingletonHwndObserver;

// Singleton message-only HWND that allows interested clients to receive WM_*
// notifications.
class GFX_EXPORT SingletonHwnd : public WindowImpl {
public:
    static SingletonHwnd* GetInstance();

    // Windows callback for WM_* notifications.
    BOOL ProcessWindowMessage(HWND window,
        UINT message,
        WPARAM wparam,
        LPARAM lparam,
        LRESULT& result,
        DWORD msg_map_id) override;

private:
    friend class SingletonHwndObserver;
    friend struct base::DefaultSingletonTraits<SingletonHwnd>;

    SingletonHwnd();
    ~SingletonHwnd() override;

    // Add/remove SingletonHwndObserver to forward WM_* notifications.
    void AddObserver(SingletonHwndObserver* observer);
    void RemoveObserver(SingletonHwndObserver* observer);

    // List of registered observers.
    base::ObserverList<SingletonHwndObserver, true> observer_list_;

    DISALLOW_COPY_AND_ASSIGN(SingletonHwnd);
};

} // namespace gfx

#endif // UI_GFX_WIN_SINGLETON_HWND_H_
